LIGGGHTS® - User Forum

Dear users,
I'm using LIGGGHTS to perform SPH simulations, and I would like to start the simulation with:

boundary f f p #periodic boundary in z direction

run it for couple of steps, and after that change the boundaries to:

boundary f f f # all fixed boundaries

and run it.

I tried with:

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run 1e5
change_box all boundary f f f remap units box
run 1e5

but it does not work. In the output file I get a message:

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.
.
Changing box ...
Setting up run ...

Hi, all

Are there any commands in LIGGGHTS that is similar to the "local damping" in PFC?
I want to use this command because the simulation is a quasi-static problem. By adopting local damping, the simulation could be greatly sped up without losing accuracy.

Many thanks,

Liu

Hello everybody,

I'm working on a very simple test-case (see input file below). Two particles, one on the top of the other with a normal spring between them (pair_style gran model/hooke/stifness) are compacted in one direction (fix comp all deform 1 z trate -1).

In the dump file, I get the expected positions and forces (components z and fz), but the velocity in the z direction (vz) is 0 for both particles at all time steps.

What am I doing wrong?

Thanks for your help.

Robin

Hi all,

I am trying to restart the simulation by changing the data file by using "read_restart tmp.restart.120000" command (120000 is the last iteration where I stopped my simulation)

But I was getting this error:

ERROR: Cannot read_restart after simulation box is defined (../read_restart.cpp:75)

Can anyone please help me in fixing this?

Thank you.

Dear users and developers,

I am simulating a simple container with an inlet and outlet (both have much smaller diameters than container diameter). I insert
particles at the upper side (in the inlet) and they fall under gravity through the container and out to the outlet.
The system boundaries are fixed and particle tracking is set to "lost" so to save computational cost (I am not interested in particles exiting the outlet, only while they are inside is what matters).

I wonder what is the difference between these two types. The sph examples available with LIGGGHTS use the 'sph' type, but the examples in SPH LAMMPS userguide use the 'meso' type.

Dear users,
currently i am working on a rotating drum mixing project. I found something is strange to me (please refer to the attached fig.). Sometimes the particles are jumping and flying. i had same issue in other mixer (the reason was due to the mesh). i have tried again playing with finer mesh. still have the same probelm. What do you think might be the reseaon? here is the parameter i am using:

Sorry for the simple question, but after searching I am unable to locate the pizza.tar.gz tar ball containing gran_pizza_17Aug10... can someone point me to this?

Hi,

I'm new to LIGGGHTS and need your help in setting up a run.
I'm getting following error,

ERROR: Mesh error: dimensions too small - use different unit system (multi_node_mesh_parallel_I.h:535)

I searched the LIGGGHTS forum and got a suggestion to change the STL file format to ASCII.
I changed the STL file format to ASCII, still the error persists.

Do you have any other suggestion to fix this error?

Best Regards,
Girish

Hello everybody,
I am a new bee to LIGGGHTS.
How can I have a book-keeping of the wall-properties of my domain? I just have to introduce a variable and I am not pretty sure about how to define it.
All I am doing is calculating the charge transfer from particle-particle and particle-wall contacts.
I am able to save the data about particle charge (q[i]=q[i]+dq) (q-charge) at each time-step.